A survey of sensing and control systems for machine and process monitoring of directed-energy, metal-based additive manufacturing

Abstract

Purpose – The purpose of this paper is to surveys classic and recently developed strategies for quality monitoring and real-time control of laser-based, directed-energy deposition.Additive manufacturing of metal parts is a complex undertaking. During deposition, many of the process variables that contribute to overall build quality – such as travel speed, feedstock flow pattern, energy distribution, gas pressure, etc. – are subject to perturbations from systematic fluctuations and random external disturbances. Design/methodology/approach – Sensing and control of laser-based, directed-energy metal deposition is presented as an evolution of methods developed for welding and cladding processes. Methods are categorized as sensing and control of machine variables and sensing and control of build attributes. Within both categories, classic methods are presented and followed by a survey of novel developments. Findings – Additive manufacturing would not be possible without highly automated, computer-based controllers for processing and motion. Its widespread adoption for metal components in critical applications will not occur without additional developments and integration of machine- and process-based sensing systems to enable documentation, and control of build characteristics and quality. Ongoing work in sensing and control brings us closer to this goal. Originality/value – This work serves to introduce researchers new to the field of additive manufacturing to common sources of process defects during metal powder-based, directed-energy deposition processing, and surveys sensing and control methods being investigated to improve the process. The work also serves to highlight, and stress the significance of novel developments in the field.